<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>
    let arr = ['jack', 'rose', 'neil', 'zhangsan', 'lisi']

    let containA = arr.filter(item =>  item.toLowerCase().indexOf('a') !== -1)
    // ['jack', 'zhangsan']  ==> [{username: 'jack'}, {username: 'zhangsan'}]
    let newArr = containA.map(item =>  ({ username: item }) )
    console.log(newArr);
  </script>
</body>
</html>